Lithium ion secondary batteries have small volume and high mass capacity density, and can supply high voltage, and therefore, they are widely employed as power supplies for small-sized equipment. For example, they are used as power supplies for mobile equipment, such as cellular phones and notebook computers. Further, in recent years, in addition to small-sized mobile equipment uses, applications to large size secondary batteries of which large capacity and long life are required, for electric vehicles (EV), the power storage field and the like, have been expected because of consideration for environmental problems, and an improvement in the awareness of energy saving.
As the negative electrode active material used in the negative electrode of a secondary battery, a carbon-based material is used. In addition, the binder used in an electrode of a secondary battery plays the role of bonding the electrode active material to each other and bonding the electrode active material to the electrode current collector. High adhesiveness, high resistance to the electrolytic solution, electrochemical stability, a simple manufacturing process, inexpensive cost, and the like are required of the binder. Examples of typical binders include polyvinylidene fluoride (PVDF). In addition, using as the binder imide-based resins typified by polyimides is disclosed (Patent Literatures 1 to 3).